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Evolution - Charles Darwin Long before the publication of...

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Charles Darwin Long before the publication of Darwin’s Origin of Species in 1859, biologists agreed that new species arise through evolution from older species…Darwin formalized the theory of how this evolution takes place. He proposed that succeeding generations of a given population will contain a higher frequency of those parental types that most successfully survive and reproduce under the existing environmental conditions… thus the frequencies of various types within the species will change over time.
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Three principles of evolution by natural selection 1. Variaiton : among individuals in a population there must be variation in morphology, physiology and behavior. 2. Heredity : variation must be heritable if differential reproduction is to alter the population’s genetic composition. 3. Selection : some forms must be more successful at surviving and reproducing than other forms in a given environment. Two different aspects of the history of life must be accounted for…
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Phyletic evolution is the successive change of form and function The extinct genus Gryphaea occurred from the Jurassic to the early Cretaceous. These fossil examples are from Brittan, but several fossil species of Gryphaea are found in the limestone of the Edwards plateau! Phyletic evolution takes place in a single line of decent.
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Diversification is the generation of many different species Figure 19-2 A variety of bivalve mollusk forms have existed at various times over the past 300 million years. At a given point in time (present included) there have been many different species each with different forms and living in different ways.
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Both phyletic evolution and diversification occur as a result of heritable variation within populations. Heritable variation is the raw material for successive change within a species and for the multiplication of new species… New genetic variation arises from various mutational processes Frequency of alleles change within populations by selective and random processes Different populations diverge because the selective forces are different or due to random drift Variation between populations is reduced by intermigration
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A diversity of species may result from adaptation Descendants of original colonizer spread to different
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